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Dyadic Green's Function (dyadic + green_function)
Selected AbstractsThird and fourth Stokes parameters in polarimetric passive microwave remote sensing of rough surfaces over layered mediaMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2008Leung Tsang Abstract We consider the four Stokes parameters in microwave emission from a layered medium with the top interface being a rough surface. The rough surface varies in one horizontal direction so that azimuthal asymmetry exists in the 3-D problem. Dyadic Green's functions of multilayered media are used to formulate the surface integral equations. Periodic boundary conditions are used. The numerical results show that the presence of the layered media below the rough surface reduces the vertical and horizontal brightness temperatures. The interaction between the rough surface and the layered media also enhance the third and fourth Stokes parameters. In particular, the fourth Stokes parameter can be large for such geometrical configurations. Results show that the nonzero third and fourth Stokes parameters exist for all frequencies and are particularly large when the rough surface has large slope. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3063,3069, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23892 [source] Vector Hankel transform analysis of a tunable circular microstrip patchINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 5 2005T. Fortaki Abstract In this paper, a rigorous analysis of the tunable circular microstrip patch is performed using a dyadic Green's function formulation. To make the theoretical formulation more general and hence valid for various antennas structures (not only limited to tunable microstrip patch); the dyadic Green's function is derived when the patch is assumed to be embedded in a multilayered dielectric substrate. A very efficient technique to derive the dyadic Green's function in the vector Hankel transform domain is proposed. Using the vector Hankel transform, the mixed boundary value problem is reduced to a set of vector dual integral equations. Galerkin's method is then applied to solve the integral equation where two sets of disk current expansions are used. One set is based on the complete set of orthogonal modes of the magnetic cavity, and the other consists of combinations of Chebyshev polynomials with weighting factors to incorporate the edge condition. Convergent results for these two sets of disk current expansions are obtained with a small number of basis functions. The calculated resonant frequencies and quality factors are compared with experimental data and shown to be in good agreement. Finally, numerical results for the air gap tuning effect on the resonant frequency and half-power bandwidth are also presented. Copyright © 2005 John Wiley & Sons, Ltd. [source] Advanced models for transient analysis of lossy and dispersive anisotropic planar layersINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 1 2010Giulio Antonini Abstract A new model is proposed for the transient analysis of the electromagnetic field propagation through anisotropic lossy and dispersive layers. The propagation equations of the electromagnetic fields are solved as a Sturm,Liouville problem leading to identify its dyadic Green's function in a series rational form. Then, the corresponding poles and residues are obtained and a reduced order macromodel is generated, which can be easily embedded within existing three dimensional solvers. The model is applied to lossy and dispersive anisotropic layers with differently polarized plane,waves. Copyright © 2009 John Wiley & Sons, Ltd. [source] A new derivation for the coefficients of the scattering dyadic Green,s function in spherically layered mediaMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 5 2007Yonghoon Kim Abstract The dyadic Green's function in spherically layered media is considered by assuming that source and field points can be located anywhere. After manipulations from the expression of the dyadic Green's function based on the reflections and transmissions of the scalar waves, the dyadic Green's function in terms of the spherical vector wave functions is newly constructed and also the coefficients of the scattering dyadic Green's function are derived in a simple form. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1142,1143, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22374 [source] Loss inclusion via dyadic Green's function modifications for microstrip structures with complex media: Interfacial exponential field behavior within conductor ,MICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2001Clifford M. Krowne Abstract 2-D field behavior within a metal strip is used to correct the dyadic Green's function for a microstrip structure containing complex-layered media so that the attenuation constant can be determined. In the x -direction, the field is built to display exponential dependence. The strip width is explicitly taken into account, along with the metal thickness and conductivity. New Green's function expressions of the structure are found consistent with a full-wave electromagnetic code employing zero thickness extent conductors for the guiding metal. Implications for numerical implementation are covered. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 54,60, 2001. [source] An extended Huygens' principle for modelling scattering from general discontinuities within hollow waveguidesINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 5 2001Ronald L. Ferrari Abstract The modal fields, generalized scattering matrix (GSM) theory and dyadic Green's functions relating to a general uniform hollow waveguide are briefly reviewed in a mutually consistent normalization. By means of an analysis linking these three concepts, an extended version of the mathematical expression of Huygens' principle is derived, applying to scattering from an arbitrary object within a hollow waveguide. The integral-equation result expresses the total field in terms of the incident waveguide modal fields, the dyadic Green's functions and the tangential electromagnetic field on the surface of the object. It is shown how the extended principle may be applied in turn to perfect conductor, uniform material and inhomogeneous material objects using a quasi method of moments (MM) approach, coupled in the last case with the finite element method. The work reported, which indicates how the GSM of the object may be recovered, is entirely theoretical but displays a close similarity with established MM procedures. Copyright © 2001 John Wiley & Sons, Ltd. [source] Optimization of integrated circuits placement for electric field reduction inside telecommunications equipment using Monte Carlo simulation and parallel recombinative simulated annealingMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2007Sotirios K. Goudos Abstract This article presents a novel approach to the modeling and reduction of electromagnetic interference (EMI) caused by radiated emissions of integrated circuits (ICs) inside rectangular metallic enclosures of telecommunications devices. This type of analysis applies for several types of modern telecommunications equipment found in high-speed networks as well as in mobile communications. A generic model of such a device is created. The ICs are modeled as small electric dipoles and their interaction with the enclosure walls is studied by using the dyadic Green's functions. The electric field on the enclosure walls is computed and its reduction is studied as optimization problem using evolutionary algorithms. Two algorithms are employed: Genetic algorithms (GAs) and parallel recombinative simulated annealing (PRSA). PRSA is a hybrid evolutionary strategy that inherits properties from both GAs and simulated annealing. Monte Carlo simulation is subsequently applied to the optimization results to derive the electric field on the metallic walls and also to perform a worst-case analysis. The applications of the above approach in early PCB design process are discussed. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3049,3055, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22893 [source] | ||||||||||